$ { \left[\begin{array}{r}{1} \\ {2} \\ {1}\end{array}\right]-\left[\begin{array}{r}{0} \\ {4} \\ {-2}\end{array}\right] = {?} } $
To find the difference of two matrices, subtract the corresponding items between each matrix. ${\left[\begin{array}{r}{1}-{0} \\ {2}-{4} \\ {1}-{-2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{r}{1} \\ {-2} \\ {3}\end{array}\right]}$